1. Field of the Invention
The present invention relates to a thin-film magnetic head, and, more particularly, to a technology which is suitable for preventing smearing of a surface of the thin-film magnetic head which slides with respect to a medium or a surface of the thin-film magnetic head which opposes the medium, and which is suitable for preventing smearing in a lapping process in a method of producing the thin-film magnetic head.
2. Description of the Related Art
Since, in thin-film magnetic heads having a magnetoresistive element, tracks can be made even more narrower than those in conventional bulk-type magnetic heads, thin-film magnetic heads are used in various forms, such as sliding magnetic heads which are constructed so as to slide relative to a tape having a high recording density, and flying magnetic heads which move relative to a magnetic disk while they are separated therefrom.
A sliding magnetic head which has a conventional thin-film magnetic head structure will be described with reference to FIGS. 19 to 23.
FIG. 19 is a perspective view of a conventional sliding magnetic head. FIG. 20 is a schematic plan view of a main portion of the sliding magnetic head as viewed from a side of a surface of the sliding magnetic head opposing a medium. FIG. 21 is a sectional view taken along line XXIxe2x80x94XXI of FIG. 20. FIG. 22 is an enlarged plan view of an MR element 105 shown in FIG. 20 and the vicinity thereof.
A sliding magnetic head B shown in FIG. 19 is formed in the following way. Side end surfaces of block-shaped core bases 202 and 203 are adhered together through a core-incorporated layer 205 to form an integral structure which is block-shaped as a whole. Then, one of the side surfaces of each of the core bases 202 and 203 (which are adhered together) are adhered and secured to a base plate 201 so that one side of each of the core bases 202 and 203 protrudes slightly outwardly from an end of the base plate 201.
One surface of the sliding magnetic head B protruding outwardly from the base plate 201 is formed into a protruding, curved shape. As shown by the phantom lines in FIG. 19, this surface is formed as a surface 206 which slides with respect to a magnetic recording medium such as a magnetic tape.
As shown in FIGS. 20 and 21, a write head (hereinafter referred to as xe2x80x9cinductive headxe2x80x9d) 210 used to perform a recording operation and a thin-film magnetic read head 211 which includes a magnetoresistive element are incorporated in the core-incorporated layer 205.
The thin-film magnetic read head 211 is formed by successively placing upon the core base 202 a lower shield layer 101, a lower insulating layer 104, a magnetoresistive (MR) element 105, an upper insulating layer 106, and an upper shield layer 107.
As shown in FIG. 20, ends of the lower shield layer 101, the lower insulating layer 104, the MR element 105, the upper insulating layer 106, and the upper shield layer 107 are exposed at the surface 206.
Here, a read magnetic gap G is formed by the lower insulating layer 104 and the upper insulating layer 106. The upper shield layer 107 and the lower shield layer 101 are formed of, for example, an alloy of nickel and iron, and the upper insulating layer 106 and the lower insulating layer 104 are formed of, for example, Al2O3.
In the structures shown in FIGS. 20 and 21, the upper shield layer 107 is also a lower core layer of the inductive head 210 which is formed thereabove. A write gap layer 110 is formed above the lower core layer (or the upper shield layer) 107. A coil layer 111 which is formed into a pattern so as to form a spiral in a plane is formed on the write gap layer 110, and is surrounded by a coil insulating layer 112. On the surface 206, an end 113a of an upper core layer 113 formed on the coil insulating layer 112 opposes the lower core layer 107 through the write insulating layer 110 so as to be separated by a very small distance from the lower core layer 107. A base end 113b of the upper core layer 113 is magnetically connected to the lower core layer 107. A protective layer 116 is formed on the upper core layer 113. In FIG. 21, reference numeral 108 denotes a detecting electrode which is connected to the MR element 105. The electrode 108 is wired on both sides of the MR element 105.
More specifically, as shown in FIG. 22, the MR element 105 comprises a magnetoresistive film (MR film) 105a and bias layers 105b and 105b. The MR film 105a is used to read out magnetically recorded data from a medium by the magnetoresistive effect. The bias layers 105b and 105b are provided on both the left and right sides of the magnetoresistive film 105a so as to cover ends of the magnetoresistive film 105a. 
Edges 105c and 105c are formed on both sides of the MR element 105. Therefore, as shown in FIG. 22, the thickness of the upper insulating layer 106 is S1, but the thickness of the portions of the upper insulating layer 106 corresponding to the locations of these edges 105c and 105c are S2, which are smaller than S1.
When the sliding magnetic head B slides with respect to a medium, such as a magnetic tape, which moves in the direction of arrow T1 shown in FIG. 22, magnetically recorded data is read out from the medium. When a guard bandless recording operation is carried out using a helical scanning type magnetic recording/reproducing device, what is called an azimuthal recording/reproducing operation (which is carried out by tilting a magnetic gap by a predetermined angle (that is, an azimuthal angle in the widthwise direction of a track) is carried out. Therefore, the medium, such as a magnetic tape, moves in the direction of arrow T2 shown in FIG. 22.
The sliding magnetic head B is produced, for example, in the following way.
Using a technique for forming a thin layer, the thin-film magnetic head 211 (which comprises the MR element 105) and the inductive head 210 are successively formed on the core base 202 in order to form the core-incorporated layer 205.
Here, as shown in FIG. 23, a method of producing the MR element 105 and the vicinity thereof is carried out to form the lower insulating layer 104, bias layers 105bxe2x80x2 and 105bxe2x80x2, and MR films 105axe2x80x2 and 105axe2x80x3 on the lower shield layer 101. A pattern, such as a resist pattern, is used to cover the bias layers 105bxe2x80x2 and 105bxe2x80x2 and the MR films 105axe2x80x2 and 105axe2x80x3. After removing the MR film 105axe2x80x3 and part of the bias layers 105bxe2x80x2 and 105bxe2x80x2 by milling, the upper insulating layer 106 is placed thereon, as shown in FIG. 22. Here, the MR film 105axe2x80x3 is completely removed by use of ion milling process, so that the bias layers 105bxe2x80x2 and 105bxe2x80x2 are formed with the corresponding edges 105c, as shown in FIG. 22.
A different core base, that is, the core base 203 is joined to the core-incorporated layer 205 in order to form a core block. One surface of the core block is lapped by, for example, a lapping tape which has diamond grains distributed thereon in order to process the protruding, curved shaped surface 206, whereby the sliding magnetic head B is formed.
Even non-contact, flying magnetic heads used with, for example, hard disks, are constructed so as to include an MR element such as that described above. Accordingly, even in producing such flying magnetic heads, the lapping process is carried out after the formation of the MR element. In the lapping process, a lapping tape, such as that described above, is used in order to lap the surface of the magnetic head which faces the magnetic recording medium.
However, in the sliding magnetic head B, the upper shield layer 107 and the lower shield layer 101 which sandwich the upper insulating layer 106 and the lower insulating layer 104 are formed of an alloy of nickel and iron which has relatively low hardness. Therefore, when the core block is lapped with a lapping tape, the lapping surfaces of the upper and lower shield layers 107 and 101 are stretched like candy by the lapping tape, so that, as shown in FIG. 20, tongue-shaped drooping portions D may be formed.
These tongue-shaped drooping portions D may, for example, reach the MR element 105 from the upper shield layer 107 or the lower shield layer 101, causing shorting of the upper shield layer 107 and the MR element 105 or the lower shield layer 101 and the MR element 105, that is, causing what is called smearing to occur.
Even when reproducing magnetically recorded data by sliding the magnetic tape or the like relative to the sliding magnetic head B, the surface 206 of the head is lapped by the magnetic tape. Therefore, as described above, portions of the shield layers 101 and 107 get stretched like candy, causing the drooping portions D to be formed, so that shorting occurs. In other words, smearing may occur.
When carrying out an azimuthal recording/reproducing operation by the aforementioned helical scanning (in which a magnetic gap is tilted by an azimuthal angle), as shown in FIG. 22, the portions of the upper insulating layer 106 corresponding to the edges 105c of the MR element 105 are thin with the thicknesses of S2, making it more likely for smearing to occur at these portions.
Moreover, in recent years, in order to respond to the demand of higher magnetic recording density, the separation between the upper and lower shield layers 107 and 101, that is, the size of the magnetic gap G needs to be made small, so that there is a tendency to form the upper and lower insulating layers 106 and 104 with an even smaller thickness. In this case, even the formation of a small drooping portion easily causes shorting of the upper shield layer 107 and the MR element 105 and the lower shield layer 101 and the MR element 105, so that it is even more likely for smearing to occur.
Even non-contact, flying magnetic heads used with, for example, hard disks are constructed so as to include an MR element such as that described above. Therefore, when an MR element is lapped in the lapping process which is carried out when producing non-contact, flying magnetic heads, smearing may occur.
In view of the above-described problems, it is an object of the prevent invention to make it possible to achieve at least one of the following:
1) To reduce the occurrence of smearing in a sliding thin-film magnetic head;
2) To reduce the occurrence of smearing that occurs when carrying out an azimuthal recording/reproducing operation by helical scanning; and
3) To reduce the occurrence of smearing in a lapping process which is carried out in producing flying thin-film magnetic heads.
To this end, according to a first aspect of the present invention, there is provided a thin-film magnetic head including a magnetoresistive element for reading out information as a result of sliding relative to a magnetic recording medium. The thin-film magnetic head comprises a base, a lower shield layer that is formed on the base, a lower insulating layer that is formed on the lower shield layer, the magnetoresistive element that is formed on the lower insulating layer, an upper insulating layer that is formed on the magnetoresistive element, and an upper shield layer. In the thin-film magnetic head, on a surface that slides with respect to the medium, the magnetoresistive element is disposed in a sandwiched state between the upper insulating layer and the lower insulating layer. In addition, a middle insulating layer is formed on both sides of the magnetoresistive element in a widthwise direction thereof so as to be positioned in a same film plane as the magnetoresistive element.
The magnetoresistive element may comprise a magnetoresistive film and a bias layer, the bias layer being positioned on both sides of the magnetoresistive film, on the surface which slides with respect to the medium, and being directly connected to the magnetoresistive film. In addition, the bias layer and the middle insulating layer may be connected together on the surface which slides with respect to the medium.
According to a second aspect of the present invention, there is provided a thin-film magnetic head including a magnetoresistive element for reading out information as a result of moving relative to a magnetic recording medium. The thin-film magnetic head comprises a base, a lower shield layer which is formed on the base, a lower insulating layer which is formed on the lower shield layer, the magnetoresistive element that is formed on the lower insulating layer, an upper insulating layer that is formed on the magnetoresistive element, and an upper shield layer. In the thin-film magnetic head, on a surface which opposes the medium, the magnetoresistive element is disposed in a sandwiched state between the upper insulating layer and the lower insulating layer. In addition, a middle insulating layer is formed on both sides of the magnetoresistive element in a widthwise direction thereof so as to be positioned in a same film plane as the magnetoresistive element.
The magnetoresistive element may comprise a magnetoresistive film and a bias layer, the bias layer being positioned on both sides of the magnetoresistive film, at the surface that opposes the medium, and being directly connected to the magnetoresistive film. In addition, the bias layer and the middle insulating layer may be connected together at the surface which opposes the medium.
According to the present invention, there is provided a thin-film magnetic head including a magnetoresistive element for reading out information as a result of sliding or moving relative to a magnetic recording medium. The thin-film magnetic head comprises a base, a lower shield layer that is formed on the base, a lower insulating layer, the magnetoresistive element, an upper insulating layer that is formed on the magnetoresistive element, and an upper shield layer. In the thin-film magnetic head, in order to make the separation distance between the upper shield layer and the lower shield layer uniform in the vicinity of the magnetoresistive element, a middle insulating layer is formed in a same film plane as the magnetoresistive element.
In the present invention, the magnetoresistive element may comprise a magnetoresistive film and a bias layer. The bias layer is positioned on both sides of the magnetoresistive film in contact therewith. The bias layer is connected to the middle insulating layer.
In the present invention, by forming the middle insulating layer in the same film plane as the magnetoresistive element, the upper insulating layer can be substantially uniformly placed along the vicinity of a portion from the middle insulating layer to the magnetoresistive element. Therefore, on the surface of the magnetic head that slides with respect to a medium or the surface of the magnetic head that opposes the medium, the thicknesses of the insulating layers between the upper shield layer and the lower shield layer can be made uniform in the vicinity of the magnetoresistive element. Consequently, even in the case where a magnetic head that performs an azimuthal recording/reproducing operation by helical scanning (in which the aforementioned azimuthal angle is provided) is used, the separation between the upper shield layer and the magnetoresistive element and the separation distance between the lower shield layer and the magnetoresistive element can be properly set. Accordingly, it is possible to reduce the tendency with which smearing occurs due to the azimuthal angle when the shield layers are stretched by the sliding of the head and the magnetic recording medium, such as a tape, relative to each other.
Accordingly, even if the separation between the upper shield layer and the lower shield layer, that is, the size of the magnetic gap is made small, it is possible to reduce the occurrence of smearing.
In the present invention, by joining the middle insulating layer to the edges of the bias layer, the boundaries between the magnetoresistive film, the bias layer, the middle insulating layer, and the upper insulating layer can be made smooth, so that the thickness of the upper insulating layer can be set substantially constant. This makes it possible to smoothly form the upper shield layer in the vicinity of the portion where the magnetoresistive film, the bias layer, and the middle insulating layer are joined together. Therefore, even when a magnetic head which performs an azimuthal recording/reproducing operation by helical scanning where the aforementioned azimuthal angle is provided is used, the separation distance between the upper shield layer and the magnetoresistive element and that between the lower shield layer and the magnetoresistive element can be separated by proper distances. Accordingly, it is possible to reduce the tendency with which smearing occurs due to the azimuthal angle when the shield layers are stretched by the sliding of the head and the recording medium, such as a tape, with respect to each other.
By virtue of each of these structures, the separation distance between the upper shield layer and the magnetoresistive element and that between the lower shield layer and the magnetoresistive element can be properly set. Consequently, it is possible to reduce the occurrence of smearing in the lapping step that is carried out to produce a sliding thin-film magnetic head or a flying thin-film magnetic head.